The present invention relates to a label printer applicator. More particularly, the present invention pertains to a tamp pad for a label printer applicator that uses web fed labels and applies those labels to a series of objects.
Automated label printer applicators or label machines are well known in the art. Such a machine feeds a continuous web of label material (which web material includes a carrier or liner and a series of discrete labels adhered to the liner at intervals along the liner), removes the labels from the liner and applies the labels to the objects. In many such machines, the label is also printed by the device, prior to separation from the liner and application to the objects.
Known label machines include, generally, a supply roll on which the web is wound. The web is fed from the supply roll around a plurality of rollers and enters a printing head. In the printing head, indicia are printed on to the individual labels. The web exits the print head and the labels are separated from the liner and are urged into contact with a tamp pad.
The tamp pad is, typically, a vacuum assisted assembly that holds the individual labels and moves the labels into contact with the objects onto which they are adhered. Tamp pads are typically designed to apply a predetermined or desired force upon application of the label to the object. The force used to apply the label can be varied depending upon the object. For example, while a relatively larger force can be used to apply a label to a heavy gauge shipping carton, a much lesser force must be used when applying a label to, for example, a bakery carton.
Subsequent to separating the labels from the liner, the liner is accumulated onto a rewind or take-up roll for subsequent disposal. The driving force for moving the web through the label machine is provided by a motor that drives supply roll while the driving force for collecting the liner is provided by a motor that drives the take-up roll.
Labeling machines are generally part of a high-speed overall processing system. As such, it is desirable to be able to detect various conditions of the supply roll, such as a low label level, few labels remaining or a no labels remaining level. In one known supply roll level sensing arrangement, an optical sensor is mounted adjacent the supply roll. The sensor is mounted so that the point at which a particular, given condition is sensed can be mechanically adjusted, such as by a two-position block or turn screw. A separate sensor in this arrangement is required for label out.
One drawback to this arrangement is that a typical mechanical mounting limits the range to which the settings can be adjusted. As such, it may be found during operation that it is desirable to set a label out or low label condition outside of the permitted range. In addition, many labels use material that has a somewhat reflective nature, and the reflectiveness of the label material can adversely effect the adjustment as well as the sensing capabilities of many such optical sensors.
Another known level sensing arrangement uses a mechanical wheel that rides on the edge of the supply roll. This system provides a continuous sensing, rather than set point sensing conditions, to, for example, indicate low and/or label out conditions. However, in order to accommodate labels having various lengths, the mechanical changes required in the sensing arrangement can be quite difficult to accomplish.
Still another condition sensing device uses an ultrasonic transducer to detect a variety of low and label out conditions. Such ultrasonic devices require considerable and sometimes complex set up times in order to properly calibrate the sensor. Additionally, these sensors typically suffer from performance degradation with changes in temperature and humidity.
In operation of a label machine, it is necessary to properly tension the liner to create optimal peel tension for separating the label from the liner backing. Such tension controls also control the windup or take-up of the waste liner onto the take-up roll.
Known machines utilize a number of different arrangements for creating the proper tension on the liner. In one such arrangement, the rewind roll includes a clutch to allow the motor drive to “slip” once a desired tension is achieved. While such an arrangement works well, the clutch requires initial tension adjustment as well as correction over time as the clutch wears. In that clutches are by nature wear-susceptible components, such clutches must be replaced during the course of operation of the machine. Typically, clutch replacement is a fairly labor-intensive undertaking and requires that the machine be taken out of service for an extended period of time.
In addition, a clutch can be set at a single fixed tension value. However, in order for the liner tension to remain constant as the roll size grows or shrinks, the clutch tension must be changed with a change in the roll diameter.
Another known arrangement for creating proper tension uses a dancer arm with a limit switch. In such an arrangement, the rewind motor is controlled to operate when the arm moves away from a set point, which set point is determined by a spring tension. In such an arrangement, the motor is either on or off with the position of the limit switch. Typical motors are AC induction-type motors.
One drawback to this arrangement is that “spikes” in the tension of the liner are observed when the motor turns on or off. In that the motor is either on and running at a particular speed, or off, it has been found that as the motor accelerates and tension increases, the desired tension set point is over-shot. This can result in tension spikes which can cause the liner to break and/or print “stretching”.
Also in known machines, in applying the label to the product or object surface, it is desirable to apply the label at a consistent force without taking into account changes in the product surface distance, reflectivity or tamp pressure. As set forth above, the label is separated from the liner and is held on the tamp pad. The label remains on the pad until the target object is in line with the pad. A tamp cylinder then extends to move the tamp pad into contact the object surface to apply the label to the surface. At the completion of the extension stroke, the cylinder returns the pad to the home or rest position at which time a subsequent label can be fed onto the tamp pad.
It is desirable to transfer the label and apply the label to the product surface at a relatively high rate of speed. As such, the transfer process inherently controls the throughput of the label machine. A number of methods are known for controlling the application of the label to the product or object surface in order to maintain high rates of throughput. One straightforward method uses a timer (through hard wiring, such as relays or through software), to return the cylinder from the extended position to the home position based upon a predetermined duration of time. While this method and arrangement is relatively straightforward, it does not compensate for varying product distance. As such, the tamp pad may not reach a shorter product, or conversely, the force may be too great for applying a label to a larger object, in which instance the force of the tamp pad could deform the product or jam the cylinder.
Another tamp pad control arrangement uses optical sensors that sense the product as the tamp cylinder is extending. Difficulties have been encountered with these optical sensors when used in connection with products having non-reflective or other than flat surfaces. In addition, because of the wiring and/or circuitry required on the moving tamp pad, mean time between failures has been shown to decrease, thus requiring maintenance and/or repair more frequently than acceptable.
Still another arrangement uses contact plates or mechanical pressure switches to sense pressure. In such an arrangement, the cylinder is returned from the extended position to the home position without a time delay, based upon a sensed pressure. These arrangements measure the pressure within the cylinder chamber and reverse direction of the cylinder upon reaching a set, high pressure point.
Typically, in these arrangements, the contact plates require a fairly significant force to perform the switch-over function, that is to sense the increased pressure in the cylinder and reverse the cylinder direction. In addition, these mechanical components add significant weight to the tamp pad which increases the time required to change direction. These arrangements typically result in a high force of application on the product surface. As with the other arrangements, this arrangement often requires operator adjustment and frequent maintenance in order to maintain the equipment in proper operating condition.
The tamp pads are configured such that a label is transferred onto the pad after it is separated from the liner with the non-adhesive side of the label contacting an impact plate (on the front side of the pad). The label is held on the plate and the tamp pad is extended toward the product surface for application of the label. In a typical arrangement, a vacuum is used to secure the label to the impact plate. Typical impact pads are formed from a low friction material having a plurality of vacuum openings formed therein. Vacuum channels are formed in the rear of the plate.
The plate is mounted to a mounting plate (the rear of the tamp pad) through which a vacuum port provides communication from a vacuum source to the rear of the impact plate. A vacuum is drawn through the vacuum openings to secure the label to the impact plate after separation from the liner and prior to application to the object surface.
Desirably, label machines are configured for accepting and applying a wide variety of label sizes. To this end, tamp pads must be configured for each of the different label sizes that may be used in a particular machine. The pads must be changed out each time the label size is changed. It has been found that use of improper pad sizes can adversely effect operation of the machine. For example, if a label is smaller than the area encompassed by the vacuum openings, the vacuum will tend to draw through those openings surrounding the label. As such, the label may not be properly secured to the tamp pad. As a result, the label can tend to slip from the pad or be misapplied to the object.
To this end, label machines are often supplied with a variety of different tamp pad sizes to accommodate label of different sizes. This increases costs as well as the time necessary for machine set up. Other arrangements use standard backing plates or mounts, but use a variety of rubber or similar material faceplates that can be punched out for the particular label dimensions. This, again, lacks the ability to reconfigure face pads that have been punched for a desired application.
Accordingly, there exists a need for an improved label printer applicator that provides a ready count or indication of the one or more desired levels of labels remaining on the supply roll. Desirably, such indication can be easily changed, and can further be used to control operation of the machine. Such a printer applicator also includes an assembly to control the movement and timing of the tamp pad with respect to applying labels to the surface of objects. Desirably, such an assembly permits applying labels to objects having varying heights or distances from the tamp pad home position, while taking into consideration the force at which the label is applied. Most desirably, such an assembly is self calibrating to take such height differences as well as changes in compressed air supply into account in applying the labels.
In such a machine, the tamp pad is configured to permit the use of different sizes of labels without the need to change-out pads for each label size. Such a machine also uses a novel rewind assembly and drive to provide proper tension on the liner to prevent over tensioning (and possible breakage), while providing sufficient tension to peel the labels away from the liner on which they are carried.